/**
 * Copyright 2010-2011 initialize4j.org
 * 
 * <pre>
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * </pre>
 * 
 * <pre>
 * http://www.apache.org/licenses/LICENSE-2.0
 * </pre>
 * 
 * <pre>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 * </pre>
 */
package org.initialize4j.service;

import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.util.Arrays;
import java.util.List;

import org.initialize4j.Initialize;
import org.initialize4j.annotations.WhenCondition;
import org.initialize4j.annotations.impl.Satisfiable;
import org.initialize4j.modify.Modifier;
import org.initialize4j.modify.ProviderModifier;
import org.initialize4j.modify.ValueModifier;
import org.initialize4j.provide.Provider;

/**
 * Implementation of the {@link InitializeService} interface.
 * 
 * @author <a href="hillger.t@gmail.com">hillger.t</a>
 */
class InitializeServiceImpl implements InitializeService {

  /**
   * {@inheritDoc}
   */
  public final <T> T create(Class<T> clazz) throws InitializeException {
    try {
      T instance = clazz.newInstance();
      initialize(instance);
      return instance;
    }
    catch (Exception e) {
      throw new InitializeException(e);
    }
  }

  /**
   * {@inheritDoc}
   */
  public final void initialize(Object bean, String... scopes) throws InitializeException {
    for (Field field : bean.getClass().getDeclaredFields()) {
      handleFieldInit(bean, field, scopes);
    }
  }

  /**
   * Handles the field initialization of a given object.
   * 
   * @param object The object in the scope of initialization.
   * @param field The field which maybe gets initialized.
   * @param scopes An optional list of scopes to allow.
   */
  private void handleFieldInit(Object object, Field field, String... scopes) throws InitializeException {
    if (field.isAnnotationPresent(Initialize.class)) {
      Initialize anno = field.getAnnotation(Initialize.class);

      Object value = InitializationUtil.getFieldValue(object, field);

      // Precondition fails or no valid scope detected
      if (!isPreConditionSatisfied(value, field) || !isScopeSatisfied(anno, scopes)) {
        return;
      }

      switch (anno.use()) {
        case PROVIDER: {
          Provider<?> provider = InitializationUtil.instance(anno.provider());
          Modifier modifier = new ProviderModifier(provider);
          modifier.change(object, field);
          break;
        }
        case CONVERTER: {
          Modifier modifier = new ValueModifier(anno.value());
          modifier.change(object, field);
          break;
        }
      }
    }
  }

  /**
   * Returns <code>true</code> if some defined precondition is satisfied.
   * 
   * @param value The value to inspect.
   * @param field The field to inspect.
   * @return <code>True</code> if the condition is satisfied -
   *         <code>false</code> otherwise.
   * @throws InitializeException
   */
  @SuppressWarnings("unchecked")
  private boolean isPreConditionSatisfied(Object value, Field field) throws InitializeException {
    for (Annotation annotation : field.getAnnotations()) {

      if (annotation.annotationType().isAnnotationPresent(WhenCondition.class)) {
        try {
          WhenCondition when = annotation.annotationType().getAnnotation(WhenCondition.class);
          Satisfiable<Object> satify = (Satisfiable<Object>) InitializationUtil.instance(when.value());
          return satify.isSatisfied(value);
        }
        catch (Exception e) {
          throw new InitializeException(e);
        }
      }
    }
    return false;
  }
  
  /**
   * Validates some optional scopes and indicates if these scopes are welcome.
   * 
   * @param initialize The specific annotation.
   * @param scopes Optional list of named scopes to validate.
   * @return True, if scope is satisfied - false otherwise.
   */
  private boolean isScopeSatisfied(Initialize initialize, String... scopes) {
    if (0 == scopes.length) {
      return true;
    }
    
    List<String> scopeList = Arrays.asList(scopes);
    for (String scope : initialize.scope()) {
      if (scopeList.contains(scope)) {
        return true;
      }
    }
    return false;
  }
}
